Electric cable and process of manufacturing same.



Patented Dec. 24, l90l.

a. E. HEYL-I IA. ELECTBIC CABLE AND PROCESS OF MANUFACTURING SAME.

Application'flled May 16, 1901.)

(No llodol.)

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" NlTE STATES ATENT FICE GEORGE EDWARD HEYL-DIA, or WARRINGTON, ENGLAND.

ELECTRIC CABLE AND PROCESS OF MANUFACTURING SAME.

SPECIFICATION forming part of Letters Patent No. 689,613, dated December24, 1901. Application filed May 16, 1901. Serial No. 60,589- (No model.)

DIA, engineer, a subject of the King of Great Britain, residing atWarrington, (private address Birk Orag, 236 Great Clowes street,

Higher Broughton,Manchester,) in the county of Lancaster, England, haveinvented certain new and useful Improvements in Processes ofManufacturing Electric Cables, (for which applications for patent inGreat Britain have been made under No.18,044,dated October 10, 1900, andNo. 19,951, dated November 6,1900; in Germany, filed January 23,1901; inAustria, filed January 24, 1901, and in Sweden, filed January 24, 1901,)of which the following is a specification.

This invention relates to electric cables,and has for its object toincrease the speaking or transmission efficiency of same when used fortelephonic and telegraphic purposes and to obtain a greater flexibility,which obviates the danger of rupture of the insulation material inbending, particularly when the cables are required for electric lightingor power.

To facilitate description, reference-will be had to the accompanyingdrawings,in which Figure 1 is a set of diagrams illustrating distortionof the usual paper strip; Figs. 2 and 3,

- a side elevation and plan of my improved paper strip; Figs. 4 and 5,perspective and crosssectional views of the conductor withlongitudinally-applied paper strip, the latter fig-. ure showing a pairof conductors laid up into a cable; Fig.6, a cross-section of severalpairs of conductors laid up into a single cable; Fig. 7, a cross-sectionof a pair of conductors with longitudinally-applied gauze; Fig. 8,asimilar view showing the'paper about the gauze;

Fig. 9, side and front elevations of rolls as used in grooving the paperstrips; Fig. 10, a front elevation of a modified form of rolls; Fig. 11,a diagrammatic view, in front elevation, of a longitudinal coveringmachine with flier for the thread-binding.

In the existing types of telephonic or telegraphic low-capacity cables,subterranean as well as submarine, every effort is made to insulate theconductor with a dielectric having a total electrostatic capacity as lowas possible, but without due regard as to how this total is made up-thatis,as to how the capacity is distributed around the conductor or betweenthe conductors in case of multiple conductors in the same cable. If across-section of such alowcapacity cable be examined,it will be found tohave an irregular form, which, moreover, will vary at different pointsof the cable if several sections be'taken, so that there is always adifferent and varying shape in the dielectric surrounding eachconductor; This is due to the old method of covering, in which theconductors are separated, for instance, by thin strips of paper, whichget distorted into all sorts of shapes, quite preventing any symmetricalarrangement of the conductors within the cable, as will be seen byreferring to Fig. l of the accompanying drawings, which showsdiagrammatically, for instance, three cross-sections at different pointsof such a cable,from which the irregular distribution of the capacitycan be seen, which produces distortion of the speaking effect.

Now according to the present invention the dielectric is alwaysdistributed uniformly about the conductor or conductors, which aremaintained symmetrically within the cable, so that there will be foundpractically the same conditions around one wire as there are around itsfellow wires, and undulatory currents can be transmitted with a minimumof distortion. By this uniform distribution of the capacity it isrendered possible in the case of long-distance telephony, for instance,to properly reproduce speech, as inductive disturbances from eitherpairs of conductors or from single wire to single wire are effectivelyeliminated, and even on short cables the speaking efficiency isincreased. This increased efficiency of my cable is due not only to theuniform distribution of the dielectric or electrostatic capacity aroundand between the conductors, but also to the less deterrent effects ofthe magnetic fields formed by current motions or Waves, which in myimproved cable are not distorted so much.

In order to attain the object of my invention, I cover the stranded orplain conductors ICO cross-hatch form on either'or .both faces, as 7'shown in Figs. 2 and 3, and folding the same longitudinally about theconductor B in the desired number of layers, with a winding of thread 0to retain the paper, as shown in Fig. 4. The conductors thus separatelycovered may be laid up in one or more pairs into a single cable, asshown in Fig. 5, and I arrange the meeting edges of the paper to welloverlap and form an increased thickness 0. at one side of each conductorand vplace this thickened part a of one conductor against thecorresponding thickened part a of its related conductor in each pair.The combined thickness d a thus produced between the two conductorsapproximates to the combined thickness of the non-thickened parts I) andof the thicker enveloping insulation 0 around the pairs, thus insuringthe same conditions and even distribution of the dielectric orelectrostatic capacity all around each conductor of the pair, as thereis an even thickness of the insulating material both around and betweenthe conductors of the cable. This cannot be attained with the usualinserted paper strip shown in Fig. 1 or with a spiral winding of thematerial on the separate conductors, which after the enveloping windingof a thicker layer would prod ucea greater thickness of insulation aboutthe pair than between the two conductors. It will be seen, moreover,that the paper touches the conductor only at numerous fine points andinsures a thorough air-space character for the cable without losing thesymmetrical arrangement of the conductor, as is the case with the usualpaper stripinsertcd between the wires, which in laying up the cablebecomes distorted, as shown in Fig. 1.

In Fig. 6 a number of pairs are shown laid up into a single cable, fromwhich it will be seen that the same advantageous conditions are producedas described with reference to Fig. 5.

The building up of the conductors into cables may be effected bysquirting paperpulp around them or wrapping on paper in the ordinaryway, or they may otherwise receive a final insulation or protectivecovering of any of the usual kinds.

The peculiar surface of my improved paper strips renders them welladapted also for the final or enveloping insulation of the cable, as notonly are uniform and ample spaces provided for air or fluid insulationby the layers only touching at numerous fine points, but

great flexibility is afforded, which is so much needed, particularlywhen the cable is to be used for electric light or power, and danger ofrupture of the insulation in bending, to which paper cables are liable,is obviated.

WVhere a gauze material is used as the preliminary wrapping for theseparate conductors,I apply it longitudinally in the same manner as thepaper with overlapping edges in order to form an increased thicknessbetween the conductors, as before described. This is shown in Fig. 7,while Fig. 8 shows the paper A longitudinally applied about the gauze D.The formation of the pyramidal 0r fine points on the paper may beeffected by suitable rolls--for instance, as shown in Fig. 9, in whichthe paper material A is passed through pressure-rolls E E, of whicheither or both are formed with peripheral ribs rnnninglongitutlinally,and then through another-pair, in which the ribs are formedtransversely, the combined effects of the two pairs being to producegrooves in cross-hatch form, resulting in the fine points illustrated inFig. 2. If the first pair of rolls be formed on the periphery withnumerous small recesses of pyramidal form, as shown in Fig. 10, thesecond pair of rolls F F may be dispensed with.

Fig. 11 illustrates, as an example, the usual longitudinal-coveringmachine for applying the paper] is the drum of wire; H, the spool ofpaper strip; I,a guide-roller; K, the folding-die, and L a flier of anyusual construction adapted to wind the thread 0 about the paper on thewire, the covered conductor being wound on a reel M.

I declare that what I claim is 1. The improvement in the process ofmanufacturing electric cables of low capacity, which consists inpreliminarily covering the conductors in a longitudinal manner with astrip of insulating material, overlapping the meeting edges of the stripto form an increased thickness along one side, binding the strip in thisposition on the conductor with a winding of thread, laying up theconductors into pairs with the said thickened parts of the relatedconductors placed together, and completing or building up the cable withthe desired number of such conductors in the usual manner, substantiallyas described.

2. The improvement in the process of manufacturing insulated electriccables or conductors, which consists in applying paper in the form of astrip havinga surface provided with grooves in cross-hatch formconstituting numerous pyramidal points, substantially as described.

3. The process of manufacturing electric ca-- bles of low capacity,which consists in preliminarily covering the conductors with a strip ofinsulating material, forming an increased thickness in said coveringalong one side, laying up the conductors into pairs with the saidthickened parts of the insulation placed together, applying an envelopof insulation about the pair of a thickness which together with thethickness of the unthickened portion of the said preliminary coveringequals the combined thickness of insulation between the two conductors,and completing or building up the cable with the desired number of suchconductors in the usual manner, substantially as described.

4. An insulated cable of low capacity, in which the preliminaryinsulating-covering of each conductor is of greater thickness along oneside, where related conductors of a pair touch one another,substantiallyas described.

5. An insulated cable of low capacity, in which the preliminaryinsulating-covering of each conductor is of greater thickness along oneside where related conductors of a pair touch one another, the combinedthickness of such insulation between the conductors being equal to thatof the enveloping insulation of the pair together with that of thennthickened portion of the preliminary covering,snbstantially asdescribed.

6. An insulated electric cable, having a preliminary longitudinalcovering of insulation in strip form with overlapped edges constitiltingan increased thickness along one side of the conductor, and havingnumerous pyramidal points on the surface of the strip which faces theconductor, substantially as described. 7

7. An electric cable, having insulation of paper provided with surfaceprojections in the form of numerous pyramidalpoints, substantially asdescribed.

8. An electric cable having insulation of paper strip provided withsurface projections in the form of numerous pyramidal points with theedges of the strip overlapping longitudinally along the conductor, and awinding of thread adapted to retain the strip in this position,substantially as described.

9. In an electric cable,the combination with a pair of conductorsarranged longitudinally side by side, of insulation for said conductors

